A new instrument constructed at the high‐pressure facility at CHESS provides a simple mechanism to group MCA data on the basis of a rapidly varying sample temperature. This system allows powder diffraction from samples at simultaneous high pressures and high temperatures in a diamond‐anvil cell. The instrument consists of a laser beam delivery system and incandescent light collection optics to analyze the resulting graybody spectra. A portion of the incandescent light controls into which multichannel analyzer group the x‐ray‐diffraction pattern accumulates. We illustrate the performance of the system with recent experiments. ©1995 American Institute of Physics.